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Issue 35, 2015
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Reduction of mixed Mn–Zr oxides: in situ XPS and XRD studies

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Abstract

A series of mixed Mn–Zr oxides with different molar ratios Mn/Zr (0.1–9) have been prepared by coprecipitation of manganese and zirconium nitrates and characterized by X-ray diffraction (XRD) and BET methods. It has been found that at concentrations of Mn below 30 at%, the samples are single-phase solid solutions (MnxZr1−xO2−δ) based on a ZrO2 structure. X-ray photoelectron spectroscopy (XPS) measurements showed that manganese in these solutions exists mainly in the Mn4+ state on the surface. An increase in Mn content mostly leads to an increase in the number of Mn cations in the structure of solid solutions; however, a part of the manganese cations form Mn2O3 and Mn3O4 in the crystalline and amorphous states. The reduction of these oxides with hydrogen was studied by a temperature-programmed reduction technique, in situ XRD, and near ambient pressure XPS in the temperature range from 100 to 650 °C. It was shown that the reduction of the solid solutions MnxZr1−xO2−δ proceeds via two stages. During the first stage, at temperatures between 100 and 500 °C, the Mn cations incorporated into the solid solutions MnxZr1−xO2−δ undergo partial reduction. During the second stage, at temperatures between 500 and 700 °C, Mn cations segregate on the surface of the solid solution. In the samples with more than 30 at% Mn, the reduction of manganese oxides was observed: Mn2O3 → Mn3O4 → MnO.

Graphical abstract: Reduction of mixed Mn–Zr oxides: in situ XPS and XRD studies

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Article information


Submitted
16 Apr 2015
Accepted
22 Jul 2015
First published
22 Jul 2015

This article is Open Access

Dalton Trans., 2015,44, 15499-15507
Article type
Paper

Reduction of mixed Mn–Zr oxides: in situ XPS and XRD studies

O. A. Bulavchenko, Z. S. Vinokurov, T. N. Afonasenko, P. G. Tsyrul'nikov, S. V. Tsybulya, A. A. Saraev and V. V. Kaichev, Dalton Trans., 2015, 44, 15499
DOI: 10.1039/C5DT01440A

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